Sorry, missed a key line when I was c&p-ing...

150/190/150 is the ratio of starter/water/flour when you refresh - the actual values depend on the amount of starter you are actually refreshing (which could be all of it if you're not baking).

You refresh the whole lot each time, adding new flour and water (well, you can throw some out, but adding refreshed sourdough to dormant sourdough doesn't really work). You then take the 290g sponge (or whatever factor of that) you need for a batch, and replace the rest in the fridge.

I'd say that for an established sourdough, a kilner jar is a good option. You want to keep it as dormant as possible while it's between bakes/refreshes, so it should be sealed and in the fridge - otherwise you risk it producing too much alcohol and killing itself. But you also don't want it to explode/buckle, which is a risk with Lock & Lock. It'll generally keep for 3 weeks like that - but it's worth draining off the fluid as it appears. After 3 weeks you need a refresh.

The pain de campagne from that recipe is delicious - the little bit of rye flour gives an extra dimension to the flavour without making the dough unworkable. It does need a proving basket, however (unless you're using a tin) as the dough isn't strong enough to self-support.